Intermittent pressure control system



Jan. 12, 1943. A. D. MacL-EAN ET AL 2,303,187

INTERMITTENT PRESSURE CONTROL SYSTEM Filed Feb. 20, 1959 Jan. 12, 1943. A. D. MacLEAN ETAL 2,308,187

INTERMITTENT PRESSURE CONTROL SYSTEM Filed Feb. 20, 1959 4 Sheets-Sheet 4 INVENTORS.

ATT

Patented Jan. 12, 1943 m'mnm'rmiv'r ranssuan coN'rnoL SYSTEM Allen D. MacLean and Fritz Nlesemann, Pittsburgh, Pa., assignors to Pittsburgh Equitable Meter Company, Pittsburgh, Pa., a corporation of Pennsylvania Application February 20, 1939, Serial No. 257,388

14 Claims.

This invention relates to fluid pressure distribution systems, and particularly to gas distribution systems in which it is desired to automatically vary the pressure in the distribution main in accordance with the consumer demand.

It is an object of the invention to provide a pressure regulating system which will be periodically responsive to increased flow in the main to boost the pressure therein in steps or stages. A further object of the invention is the provision of a fluid pressure regulating system which will not be subject to surges of pressure and may be adjusted to compensate or nullify surges which otherwise would occur.

A further object of the invention is the provision of a pressure regulating system in which the regulator is loaded in accordance with the rate of flow at periodic intervals and is maintained at such load until the next interval. The present invention is an improvement on the system disclosed and claimed in the application of Allen D. MacLean for Fluid distribution system, Serial No. 230,343, flied September 16, 1938.

As will hereinafter appear, the invention may be applied to systems employing direct acting regulators, pilot controlled, or pilot loaded regulators.

The invention will be described in connection with the accompanying drawings, wherein I have shown a preferred embodiment of the invention by way of illustration, and wherein:

Figure 1 is a partly diagrammatic view showing a preferredinodification of the system,

Figure 2 is an enlarged view of a preferred pressure differential producing device,

regulator body 3, and the compartment above the diaphragm 8 is vented to the atmosphere in the usual manner. The diaphragm 8 is weighted in any suitable manner, as for example, by weight p i2, which can be changed as desired.

Pilot control system The pilot control system comprises a conduit I! connected at one end to-the high pressure main i and at the other end to the inlet I6 of an outlet pressure regulator l'l shown partly diagrammatically in Figure 1. This regulator ll may be of any suitable construction, and comprisesprincipally a diaphragm l8 secured to a pivoted lever l8 having a valve memb r 2| at its opposite end for closing the inlet IS, the outlet 22 of the regulator connecting directly with the outlet chamber 28 under the diaphragm.

- A conduit 25 leads from the outlet of a regulator I'I to the inlet 26 or a regulator 21, and Ma throttling orifice 28 interposed therein which Figure 3 is an elevation of the interrupter L valves,

Figure 4 is a view partly in section on line IV-IV of Figure 6,

Figure 5 is an enlarged view in section of the differential responsive regulator,

Figure 6 is a plan view of Figure 4, Figure '7 is a partly diagrammatic view of a modification, and

Figure 8 is a diagrammatic view showing a modiflr ition of this system shown in Figure 1.

Referring to the drawings, the numerals l and 2 represent high and low pressure mains respectively of a distribution system with a, regulator body 3 therebetween having a reducing valve 4 therein which preferably is of the balanced yp The valve 4 as shown is connected by a fulcrumed lever 5 to the operating stem 6 of a pressure responsive device indicated generally by the numeral 1. The pressure responsive device prefsive chamber H from the pressure within the the opening 4| in the orifice plate.

may be fixed or adjustable as desired. Regulator l1 primarily serves to reduce the pressure in conduit 25 to some convenient value and when I the pressure in main I is not too variable or too high for the diaphragm 8, regulator ll may be omitted, if desired, conduit 25 being connected directly into main l. A conduit 29 is connected to conduit 25 downstream from the orifice 28 and is connected to the control chamber ll of the main regulator. The regulator 21 ha a diaphragm 33 over an outlet chamber 30 and which is secured to a pivoted lever 3| having a valve 32 at its opposite end for closing the inlet 26. The regulator 21 may be considered as an outlet pressure controlled relief valve for certain purposes and the special construction and function 01 the regulator 21 will hereinafter be described. A conduit 34 is connected from the outlet 35 of the regulator to the low pressure main 2.

Pressure difierential producing means The low pressure main 2 has a pressure differential producing device, shown diagrammatically in Figure 1 as an orifice plate 38 and an inserted Venturi section 39 positioned adjacent However, any other type of differential pressure producer may be used. The preferred pressure difierential producing device is shown in detail in Figure 2, and comprises a, hollow cylindrical body member 42 inserted in the pipe line and clamped by bolts 43 between the flange 44 of the regulator body 3 and flange 45 of the adjacent pipe section of the low pressure main. The orifice plate 38 is secured by screws, or in any other suitable manner to the internal shoulder 46 of the insert 42. The insert has a hole 41 therein through which passes the pipe or conduit 48 connected by a vent 50 with the interior of Venturi section 39,

said conduit being sealed by stumng box 49.

The inserted Venturi section consists of two 7 threaded therein which provides a piezometer connection to the exterior. The differential pressure producing device, comprising an orifice plate and inserted Venturi section herein described, is preferred because it is compact and within a very short length a great differential in pressure and excellent recovery can be produced with an overall pressure loss much less than would beproduced by an orifice plate alone required to give the same differential pressure.

Interrapter valves Conduit 58 is connected to the inlet 59 of an interrupter valve, shown diagrammatically in Figure l and indicated generally by the numeral 60. This interrupter valve 60 comprises a cylindrical body having a threaded extension 62 passing through a bore 63 in a plate 64 and held thereto by a nut 65. The plate 64 has a second bore therein which receives a second interrupter valve case 66 having a valve 61 and stem 69 therein constructed exactly like the valve 60 and held by the nut 68. As valve 66 is exactly like valve 60, only valve 60 will be described in detail. The body of valve 60 has a bore 1I through which extends a valve stem 12. The bore II -is surrounded by a packing recess 13 which receives a packing 14 that is compressed by the gland 15, the valve stem 12 extending through the gland. A second recess or inlet chamber 16 surrounds the valve stem and is in communication with the internally threaded inlet piece 11 welded or otherwise suitably secured to the body. The casing 60 is counterbored at 18 to provide a valve chamber, and a valve 19 in this chamber is secured to the valve stem 12.

The valve 19 is preferably made of a soft material, such as lead, rubber, thiokol, Duprene" or the like, and is forced over the retaining shoulder 80 by stretching.

An outlet piece 8I, suitably secured to the valve casing, communicates with the valve chamber 18. A spring 82 abutting a shoulder 83 on the valve stem 12 and a threaded cap 84 holds the valve 19 normally closed.

It will be observed that the seat 85. of the valve is conical in form, having a slight angle with the horizontal. This form is of particular advantage in conjunction with a soft valve because as the seating pressure on the-valve is increased this pressure is distributed over an increasing area which decreases the tendency of the seat to cut a groove into the valve. Even if a groove becomes worn in the valve, a new area will come Differential responsive regulator The center diaphragm 33 of the regulator 21 tends the threaded diaphragm stem 93. The

stem 93 is threaded at its lower end 94 into the threaded hole 95 of the support 96, a washer 91 being located above the diaphragm pan 9| and the assembly being held in position by a nut 98. The outer periphery of the diaphragm is held between the flanged lower casing of the regulator and an intermediate flanged case 99 having a perforate top wall I00 located above the diaphragm 23. A second flanged case IOI having a perforate bottom wall I02 is secured above case 99. The stem 93 extends through a central opening I03 in the bottom wall I02 and has two nuts, I04 and washers I05 thereon, between which is clamped a, sealing diaphragm I01. The outer periphery of this diaphragm I01 is clamped against the dividing wall I02 by a clamping ring I08 held thereon by screws I09 or in any other suitable manner. There is thus formed a sealed pressure chamber IIO between diaphragm 29 and wall I00 which has outside communication by the threaded pipe tap III.

A second operating diaphragm II 3 is secured at its outer periphery between the flanged case I0! and a cover H5 and at its center is clamped the operating stem 93 by diaphragm pans H5 and 6, nuts H1 and washers H8. Thus a second pressure chamber I2I is provided between. diaphragm II 3 and wall I02 which has outside communication by the threaded pipe tap I24. The cover II4 of the regulator has a suitable vent I26 therein, and receives a spring I21, the compression of which may be adjusted by a plug I28 threaded into the extension I 29 of the cover. The extension I29 may be sealed by a cap I 3!.

The inlet 59 of the valve 60 is connected to the conduit 59, and the outlet 8| of-this valve is connected by conduit I to the middle pressure chamber IIO of the regulator 21. The inlet I36 of valve 66 is connected to the conduit 48, and the outlet I31 is cohnected by conduit I38 to the upper pressure chamber I2I in the regulator 21. Suitable reservoirs I39 and I are connected to conduits I38 and I35 respectively to prevent rapid fluctuation of pressure in these conduits upon operation of valves 60 and 66. These tanks or reservoirs also provide a large volume of gas in conduits I38 and I35 of which they are a part, so that should small leakage occur from these conduits, the resulting loss of pressure therein will not be great and will not greatly influence regulator 21. Any other means may be provided for this purpose and in some cases, for example, when conduits I38 and I35 carry suflicient volume, these tanks may be omitted. The operation of valves 19 and 61 may be done manually or automatically in response to any desired condition.

Operating mechanism of interrupter valves In the preferred modification hereinafter described these valves are automatically timed to operate periodically at equal or unequal intervals and thus produce a boost in pressure in the main 2 in predetermined stages, which may be based on time or any other desired factor. Between boosts the regulator 1 is governed by the .presshre in the regulator outlet. Referring to Figures 4 and 6, the plate 64 which is adapted to be secured to the case of a motor or other support, carries a clevis I40 secured thereto by-screws I and is secured between two diaphragm pans 9| and which has holes I42 therethrough. An operating lever I43 has a hole I44 therethrough and a clevis pin I45 passing through the holes I42 and I44 serves as a fulcrum for lever I43. Screw I41 abuts operating bar I46 which has bores I43 at its ends which receive flanged bushings I49 having bores I50 which engage the upper ends of the stems of valves 61 and 19. When the left end of lever I43, as viewed in Figure 4, is raised, the screw I41 engages bar I46 to depress valve stems 12 and 69 to open valves 19 and 81. The raising of the left end of lever I43 preferably is accomplished by a rotating drum II having a flange I52 carrying one or more trip lugs I53. The lugs I53 may be secured thereto in any desired manner, as for example, by nuts I54 threaded onto the integral threaded stems I55 thereof.

The drum I5I preferably is operatedby a fluid motor operating at uniform speed, and for this purpose I may employ the usual type of diaphragm gas meter I51 (Figure 1) having an index shaft I58 extended therefrom upon which cylinder I5I is secured. A preferred construction of gas meter is disclosed in U. S. Patent No. 1,862,451 of James R. Armstrong, dated June 7, 1932. The gas meter is supplied with gas by conduit I59 connected with conduit 25, and it will be observed that throttling orifice 28 tends to minimize the effect that otherwise would be produced in chamber l I by reason of fiow through conduit I59 and consequent operation of regulator I1. A regulator casing IBI is connected to conduit I59 at the inlet I62, and a conduit I63 connects the outlet I54 with the inlet of motor I51. The outlet of the regulator communicates by a conduit I65 with the control chamber I66 under diaphragm I61 and a valve I68 connected to the diaphragm controls flow through the regulator.

A throttling orifice I69, which may be fixed or adjustable, is interposed in the conduit I63 between the regulator outlet I64 and a conduit IN is connected at one end through a vent I12 with a chamber I13 over the diaphragm I91. A spring I13 biases the diaphragm and valve I68 towards open position. The preferred construction of regulator IBI except for conduit I1I is like that disclosed in the application of Fritz Niesemann, Serial No. 128,192, filed February 27, 1937. The outlet of the motor I51 is connected by conduit I15 to the low pressure main 2.

' The operation of the apparatus now will be described. For illustration, it may be assumed that it is desired to carry a minimum pressure of six inches of water in the low pressure main and increase this pressure to a maximum of ten inches of water at periods of maximum demand. The weight I2, therefore, will be selected so that it will be counterbalanced by a pressure slightly more than ten inches of water in the chamber II, and valve 4 therefore will remain closed until the pressure in chamber II falls below the desired maximum. Regulator I1 is set to deliver a pressure in conduit high enough to completely close the valve 4 when the full outlet pressure of reglator I1 is applied in chamber I I, and pref erably should deliver a pressure about four to six inches of water higher than the pressure actually needed to just support the weight I2. The regulator 21 is set to close at an outlet pressure slightly above six inches of water during minimum flow through the main 2, with the differential pressure in conduits 58 and 43. which may be considered as substantially zero under minimum flow conditions, connected to chambers I2I and I I0 respectively. The orifice 28 is adjusted or selected so that under the substantially balanced condition of valve 32 a flow through the orifice will be allowed so as to maintain the pressure in the conduit 25 slightly more than ten inches of water, or suflicient-to'raise diaphragm 8 and close valve '4. This can be accomplished, for example, by having the orifice 29 about one thirty second totone sixteenth inch in diameter and having the inlet of regulator 21 about three eighths inch in diameter. Assuming valves vI51 and 19 open, should the pressure in main 2 drop below six inches due to an increased demand, the pressure at the throat of the Venturi section is reduced because of the increased flow and the differential pressure across chambers I I0 and I2I allows spring I21 to open valve 32 to permit escape of gas from conduits 25 and 29 and thus lower the pressure therein, thereby allowing weight I2 to fall and open valve 4.

This increase in fiow from the high pressure main I and the low pressure main 2 continues until the pressure in main 2 transmitted through conduit 34 to chamber 30 is sufllcient to close valve 32. Valve 32 may be considered as arelief valve for conduit 25 or chamber II and is outlet pressure controlled because controlled by the pressure in chamber 30 when the pressures in chamber III) and I2I are stabilized. This will be slightly more than six inches of water because the trapped difierential pressure in chambers I I9 and HI is less than normal at six inches. Should the differential pressure on regulator 21 become so great that a pressure higher than about nine inches of water is required to close the valve 32, this valve will remain closed because the pressure in conduit 25 and chamber II will have built up sufiiciently to close valve 4 and will hold this valve closed, so that pressure in conduit 2 cannot thereafter build up high enough to open valve 32.

Instead of having the regulator 21 responsive at all times to the difierential at the throat of the Venturi section, the interrupter valves 61 and 19 open momentarily at certain intervals and then close again so as to trap the differential pressure in chambers III) and HI of the regulator 21. As long as the valves 61 and 19 remain closed the valve 32 of the regulator remains loaded by the spring I21 and the difierential pressure trapped in the chambers III] and I2I of the regulator, and the valve 32 therefore, will remain open until the pressure in main 2 builds up sufficiently for the pressure in chamber 39 to counterbalance this loading effect and close the valve 32. Thus, the boosting action of regulator valve 4 depends on the momentary rate of flow only at certain times and between such times is stabilized so as to maintain a constant boosted pres sure in the outlet pressure until such time as the interrupter valves are again opened to stabilize the system at a different boosted pressure. Each time the interrupter valves are operated the valve 4 becomes responsive to the instantaneous difierential pressure at the Venturi section and acts to build up and maintain a corresponding pressure in the low pressure main 2. At the the pressure in main 2 because long surges ofpressure or pressure waves occurring in the main 2 cannot cause excessive increases in the boost in the main, as this boost is dependent on the trapped diflerentiafpressures in the chambers I I and I2I of the regulator 21.

The controlling motor I51 may be set to operate the interrupter valves 81 and 18 at any desired equal or unequal intervals of time, by means of the disposition of the studs I53 around the periphery of the roller II, or by varying the speed of the motor. or by both means. By suitably shaping the studs I53 and properly selecting the length of lever I43 and forming its end to conform to an are about the pivot I45 as a radius the action of valves 81 and 19 may be made quite rapid, and screw I41 will enable a certain adjustment of the duration of the opening movement of the valve. Preferably the valve operations are timed to occur at intervals of about forty-five to seventy-five seconds, and preferably the valves are held open for a lesser time than the normal lag in the system between the change in pressure in the main 2 and the response of the valve 4. However, it will be understood that the duration of valve opening and intervals between openings may be varied depending on the characteristics of the system. If desired, the motor may be timed to operate at only certain periods of the day or night, and leave the valves open at other times.

It will be understood that conduit I59 can be tapped directly into the high pressure main I or into the conduit 25. If desired, the motor I51 may be replaced by any other type of motor, such as an electric synchronous motor, or a motor having any desired action.

In the modification diagrammatically illustrated in Figure 8, wherein like parts are indicated by like reference numerals, the regulator 2 I0 has a diaphragm 2 providing a chamber II therein which is directly connected by conduit 2l2 with outlet 3 of the regulator. The stem 2I3, connected to diaphragm 2| I, is secured at its upper end to a lever 2I4 which is pivoted at its end 2I5 to a bracket 2I6 secured to the regulator casing, and the lever 2I4 is guided for movement in a forked bracket 2". A weight 2I8 is located on the lever 2I4 and may be adjusted along this lever to vary the load impressed on the diaphragm 2| I.

A differential loader 220 is secured to the pipe 2 by a bracket 22I of any suitable construction and has a diaphragm 222 therein providing differential pressure chambers 223 and 224 on opposite sides thereof. A rod 225, secured to the diaphragm 222, is secured to the free end of lever 2I4 by a suitable spring 226.

The low pressure at the throat of the inserted Venturi section 39 is transmitted by conduit 48 through valve 61 and conduit 228 to the chamber 224 of the diiferential loader, and the pressure adjacent the Venturi section 39 is transmitted by conduit 58, valve 19 and conduit 221 to the chamber 223 on the opposite side of the diaphragm 222.

In this modification the diaphragm: 2 is governed by the pressure in chamber II, which, being connected by conduit 2l2 to the outlet of the regulator 3, it will be seen that the movement of diaphragm 2I I and of valve 4 is governed by the pressure in the low pressure main 2. The movement of diaphragm 222 is governed by the diirerential pressure in chambers 223 and 224 and when valves 61 and 19 are open this differential will correspond to the difference between the pressure in main 2 and the pressure in the throat of the Venturi section 39. The effect of this diiferential is transmitted by rod 223 and spring 224 to lever 2 and acts to load or unload this lever in accordance therewith. When the motor I51 intermittently opens and closes valves 91 and 19, the diil'erential pressure is trapped in chambers 222 and 224 and influences the loading of diaphragm 2 until valves 51 and 19 are again open to change the diil'erential pressure in chambers 223 and 224. Thus, it will be seen that at all times diaphragm 2 is subject to the pressure in the main 2, by reason of its connection therewith by conduit 2 I2, and is variably loaded by the difierential loader 220 in accordance with the rate of flow in the main 2. By operating valves 61 and 19 intermittently, pulsation of diaphragm 222 is eliminated and the action of diaphragm 2 thereby is stabilized to eliminate the eifect of pulsations or fluctuations in pressure thereon. If desired, storage tanks I39 and I may be connected to conduits 221 and 228 to minimize changes in pressure due to movement of diaphragm 222.

In the modification shown in Figure 7, parts of which are diagrammatically shown and wherein like parts are correspondingly numbered, the insert 42 has a threaded bore I which receives a conduit I8I connected by a vent I82 with the interior of the insert, and at the exterior end is secured a T fitting I83 which has inserted in one branch thereof a ported body member I84 with a longitudinal channel I85 therein terminating in a restricted portion at its end which forms a valve seat I86. The conduit 48 threaded into the inserted Venturi section 39 passes through conduit I8I and is connected to channel I85 in the body I84. A connecting channel I88 in the ported body member communicates with a U- shaped pipe section I89 which in turn communicates with a suitably enlarged chamber I9I in the valve stem channel I92 f the bonnet member I93 threaded into the ported body member. A valve stem I94 extending through the channel I92 carries at its inner end the double seat needle valve I81, in a control chamber I95, tapered valve portions at its end fitting the seats I86 and I98. The valve stem has the valve operating member I91 which is graduated and may be read in connection with a suitable reference point on the bonnet. The conduit 48 communicates by the channel I85, chamber I95 and pipe I98, and through the valve 81 with the conduit I38, while the conduit I8I communicates through pipe I99 and valve 19 with the conduit I35.

The boost limiting device comprises a cross conduit 20I in the T I83 connected with the conduit I 8| at one end and at th other end with the inlet side of the back pressure regulator 282. Regulator 202, which is partly diagrammatically shown, contains a diaphragm 203 and provides a chamber 204 above the diaphragm which is open to the atmosphere and a chamber 205 under the diaphraigm .which communicates with conduit 2!. The diaphragm 203 is loaded by an adjustable spring 206 or by any other suitable means and is connected to a valve 201 which controls communication between inlet pipe 20I and outlet conduit 201 connecting with the valve chamber I95. Thus, it will be seen that valve chamber I95 can be connected with the pressure in the main 2 by closing conduit I85 by means of valve I81, or can be connected thereto by opening of valve 201. Ordinarily, valve I81 is positioned clear of seats I88 and I95 in order thereby tc govern the rate of boost.

The operation of the boost limiting device is as follows. When the pressure in the main 2 beconduit 48 to .the throat of the Venturi section.

As conduit I99 is connected to chamber I95. the pressure in conduit I98 will become substantially equal to that in passage I99 when valve 201 is open and when valves 61 and I9 are opened a zero diflerential will be impressed on chambers H and I2I to which conduits I98 and I99 are connected. The regulator 21 then becomes responsive solely to the pressure in chamber 30, which is high enough to close valve 32 and keep it closed until the pressure in main 2 falls below the maximum predetermined pressure. The predetermined limit that thus can be placed on the amount of boost desired in the system can be adjusted by means of the adjustable spring 206,

and the rate of boost can be overned by .positioning valve I81 to seat against seat I96 only or to be spaced from both seats the desired amount. This positioning of the valve I81 can be accurately gauged by the graduated handle I91.

The modification disclosed in Figure 7 is particularly applicable to the system shown in Figure l, and when used in this connection conduits I38 and I will be connected with conduits 221 and 228 respectively. When assembled in this manner it will be seen that the boost limiting device operates to equalize the pressure in chambers 223 and 224, thus eliminating their effect on the diaphragm 2, which then becomes entirely responsive to the weight 2l8, and if this weight is initially set to close the valve 4 at a predetermined pressure, the valve 4 thus will close and not re-open until the pressure in conduit '2 has fallen down to the predetermined maximum-pressure for which diaphragm 203 is loaded. When diaphragm 203 closes valve 201, a differential pressure across diaphragm 222 then again becomes established and diaphragm 2 becomes responsive to the loader 220.

In applying the invention to a pilot loading system, the outlet pressure of main 2 is led to one side of the diaphragm of a main regulator and the regulator 21 shown in Figure 5 has its inlet 26 connected to the high pressure main 2 and its outlet 35 connected to the other side of the diaphragm of the main regulator, the flow therethrough being bled to atmosphere or back into main 2 through a suitable needle valve or restricted orifice. The connections III and I24 are connected as shown in Figure 1 andthe conduit I59 in Figure l is connected to .the outlet side 35 of the regulator 21.

Having described our invention, what we claim and desire t6 secure by Letters Patent is:

1. In a fluid pressure regulating system, the combination of high and low pressure mains, a valve for controlling passage of fluid between said mains, a pressure responsive device having operating means connected to said valve, a conintermittently connecting said latter conducting means to the source of low pressure.

2. In a fluid pressure regulating system, the combination of high and low pressure mains, a valve controlling passage of fluid between said mains, a pressure responsive device having oper- "ating means connected to said valve, a conduit including an outlet pressure regulator for supplying fluid under pressure from the high pressure main at a predetermined pressure to said pressure responsive device to control the operation thereof and discharging into the low pressure main, a valve in said conduit, means responsive to the pressure in the low pressure main for controlling said valve, a source of low pressure in said low pressure main, and means for intermittently conducting the low pressure from said source upon said latter means for loading the same.

3. In a fluid pressure regulating system, the combination of high and low pressure mains, a valve controlling passage of fluid between said mains, a pressure responsive device having operating means connected to said valve, a conduit for supplying fluid under pressure to said pressure responsive device to control the operation thereof, a valve in said conduit, a flow responsive differential pressure producing device in one of said mains, means responsive to the differential pressure developed thereby to control said valve, and means for intermittently connecting said latter means to the source of differential pressure.

4. In a fluid pressure regulating system, the combination of high and low pressure mains, a

.valve for controlling passage of fluid between said mains, a pressure responsive device having valve operating means connected to said valve. means normally biasing said pressure responsive device and tending to open said valve, a conduit containing an outlet pressure controlled pilot regulator for supplying fluid at a predetermined pressure to said pressure responsive device and opposing said biasing means, an outletpressure controlled relief valve in said conduit providing escape of fluid from said conduit, a flow responsive low pressure producing device in said main, means for impressing the low pressure upon said relief valve for operating the same, and means operating at a uniform speed for intermittently applying said low pressure to the relief valve.

5. In a fluid pressure regulating system, the combination of high and low pressure mains, a

-valve for controlling passage of fluid between ter valve, means for intermittently applying the duit for supplying fluid under pressure to said lowpressure from said source to said latter means, and means for controlling the time interval of operation of said intermittent means.

6. In a fluid pressure regulating system, the combination of high and low pressure mains, a valve for controlling passage of fluid between said mains, a pressure responsive devicehaving valve operating means connected to said valve,

an outlet pressure pilot regulator having its inlet connected to the high pressure main and a conduit connecting the outlet thereof to said pressure responsive device to control the operation thereof, a fluid motor having its inlet connected to said pilot regulator outlet conduit, an outlet pressure regulator in the inlet conduit of the motor, a restriction in the inlet conduit of the motor on the downstream side of said latter pressure regulator, means connecting said latter pressure regulator with the downstream side at said restriction to produce a uniform flow of fluid to the motor whereby the motor is operated at a uniform speed, a pressure diflerential producing device, valve means in the pilot-regulator outlet conduit for relieving the pressure therein, means responsive to the diflerentlal pressure developed by the differential pressure producing device for controlling said latter valve means, and means actuated by said motorfor intermittently 1mpressing said diflerentlal pressure on the latter means.

7. In a fluid pressure. regulation system, the combination of high and low pressure mains, valve means controlling flow'of fluid between said mains, a fluid motor supplied by fluid from one of said mains, an outlet pressure regulator in the inlet conduit of the motor, a restriction on the downstream side of said pressure regulator, a conduit on the downstream side of said restriction connected to the other side of said regulator, a conduit, and valve means in said latter conduit operated by said motor.

8. In a fluid pressure regulating system, the combination of high and low pressure mains, valve means controlling flow of fluid between said mains, a fluid motor having its inlet connected to the high pressure main and its outlet connected to the low pressure main, means for maintaining said motor at constant speed of operation, a conduit, and valve means in said conduit operated by said motor.

9. In a fluid pressure regulating system, the combination of high and low pressure mains, a valve for controlling passage of fluid between said mains, a pressure responsive device having valve operating means connected to said valve, an outlet pressure pilot regulator having its inlet connected to the high pressure main and a conduit connecting the outlet thereof to said pressure responsive device to control the operation thereof, a fluid motor having its inlet connected to said regulator pilot outlet conduit, means for operating said motor at constant speed, a pressure differential producing device, valve means in the pilot regulator outlet conduit for relieving the pressure therein, means responsive to the differential pressure developed by the diflerential pressure producing device for controlling said latter valve, and means actuated by-said motor for intermittently impressing said cliiierential pressure on the latter means.

10. In a fluid pressure regulating system, the combination of high and low pressure mains, an outlet pressure regulator having its inlet connected to the high pressure main, a fluid motor,

11. In an apparatus of the character described, the combination of high and low pressure mains, valve means controlling passage between said mains, a pressure responsive device having means connected to said valve, a conduit for supplying fluid ressure to said pressure responsivedevice to control the operation thereof, a relief valve in said, conduit, a differential pressure producing device in said low pressure main, and means for loading'said relief valve by the diiferential pressure at predetermined intervals, comprising a uniformly operating motor, a conduit between said relief valve and differential pressure producing device, and valve means in said latter conduit intermittently operated by said motor.

12. In a fluid pressure regulating system, the combination of high and low pressure mains, a valve for controlling passage of fluid between said mains, a pressure responsive device having operating means connected to said valve, means for subjecting the pressure responsive device to the pressure in the low pressure mainzmeans for producing a pressure differential dependent on rate of flow, means separate from the pressure responsive device for loading the pressure responsive device in accordance with said pressure diiferential, and means for interrupting the pressure differential loading of said latter means.

13. In a fluid pressure regulating system, the combination of high and low pressure mains, valve means controlling passage of fluid between said mains, pressure responsive means to govern the operation of said valve, a conduit including an outlet pressure regulator for supplying fluid under pressure from the high pressure main at a predetermined pressure to said pressure responsive means, a second outlet pressure regulator in said conduit having a plurality of diaphragms therein for venting the pressure in said conduit, a source of differential pressure in said low pressure main, and means for intermittently conducting the differential pressure from said source to said diaphragms of said outlet pressure regulator for controlling the pressure in said conduit.

14. In a fluid pressure regulating system, the

. for supplying fluid under pressure to said pressure responsive device to control the operation thereof, an outlet pressure controlled relief valve in said conduit comprising a casing having an inlet connected to said conduit and an outlet, a valve for controlling flow between said inlet and outlet, a diaphragm connected to said valve and providing a control chamber in direct communication with said outlet, a dividing wall providing a confined chamber on the opposite side of said diaphragm, a second diaphragm providing a cona conduit connected from the regulator outlet to the fluid motor, a conduit connecting 'the fluid motor outlet to the low pressure main, a second outlet pressure regulator in the inlet conduit of the motor comprising a diaphragm subject to the side of the diaphragm of said regulator whereby the motor is operated at uniform speed.

fined chamber on the opposite side of said dividing wall, means connecting said diaphragms for conjoint movement, means for sealing said connecting means with relation to said dividing wall,

.-a source of differential pressure in said low pressure main and means intermittently connecting said difierential pressure across said dividing wall. 7

ALLEN D. MACLEAN. FRITZ NIESEMANN.

. cmmmcum OF com-momen Patent no. 2, 508,187. Jenuery 12, 1915.;

ALIEN D. nacLEAn, ET AL.

' A It is hereby certified that er'rorappeare in the printed specification of the above numbered patent requiring correction as follows: Page 5, second column, line 50, claim 5', before "valve" insert --second--; and that the said Letters .Patent should be read with this correcticn therein that the name may conform to the record of the ca se in the Patent Office.- Signedend sealed this 9t dayof March, A. n. 1915.

Henry Van Arsdale, (seal) Acting Cmmnissioner of Patents. 

